Recently brewed a dry stout extract kit. Boiled 5 gallons on propane. Steeped 2 lbs of roasted malt, crystal malt and flaked barley at 155-160 F. Extract was 6.6lbs of Coopers Light LME. As usual, I swirled about a cup of near boiling water in the extract cans to get the "leftovers". Recipe's expected OG was 1.050. Measured OG after topping off to 5 gallons and just before pitching was 1.060. Temp was around 68.

As a test of the recipe, I plugged everything into BeerSmith and (if I did it right) it estimated a OG of 1.052.

I ended up just pitching the yeast. I supposed I could have kept adding top-off until I got down to 1.050.

Any thoughts on what I could have done to get a OG of 1.060 instead of 1.050? Thanks.

3 Answers
3

Its likely that you got a little more out of your grain then the original recipe intended. Furthermore, I think you underestimate the precision of your hydrometer. The standard error in our measurements with a hydrometer is probably not far from the 0.008 you are off from what beersmith told you.

Within all practical purposes you hit your target gravity on the nose when you take into account the variability of the measurement and the factors that go into it. I'd be more concerned if you had gotten 1.030 or 1.080.

Do you think the uncertainty in your hydrometer measurement would be really that high? Providing that you calibrate the reading to the correct temperature I don't see why you can't do significantly better than that. The graduation on my hydrometer is 0.002, so as long as you can clearly see the meniscus your uncertainty is not going to me more than +- 0.002.
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PoshpawsJul 3 '11 at 15:12

Interesting. I AM worried about the precision of a roll of paper shoved into a glass tube. I would imagine that inaccuracies would be consistent and linear tho. I have a refractometer that I was using for salt water aquarium. Tried once before with wort but couldn't get any reading.
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Bob BanksJul 3 '11 at 17:17

Don't knock the technology - simple is beautiful! Assuming it is a half-decent hydrometer then it should be calibrated to a (known) temperature. This is sometimes 20C/68F. Within a reasonable temperature range the correction is linear. To get a 0.01 systematic offset due to temperature, your test liquid would have to be at about 120F.
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PoshpawsJul 3 '11 at 18:47

There are more variables than the hydrometers calibration. CO2 in the beer, temp of beer, solids in beer, bubbles at the top. These are small, but the contribution to error multiplies. Its not huge but its there. I am not say the OP isn't being careful (his post suggests the opposite). I am just saying that the real FG and what our little home-hobby equipment tells can be different. A difference of +/- 0.008 is not that different, certainly in taste. The OP also seems to be really careful. I am certain he did a better job than most of getting every last drop out of the extract containers.
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brewchezJul 3 '11 at 20:45

I think it should also be appreciated that the people that formulated the recipe, or what a software program says you should get, are going to be different that what your software says, or what your hydrometer gets. Lastly, there could be dissolved solids in the water used compared to when the kit was made. These things all certainly contribute to a potential difference. We should take these #'s as sacrosanct. A +/-0.008 difference is nothing.
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brewchezJul 3 '11 at 20:47

A difference of 0.01 in OG looks suspiciously like the difference you'd get in your recipe if you used DME rather than LME (the quoted difference is usually 20% - i.e., DME contains 20% more fermentable sugars by weight).

There was only a .002 difference between the recipe provided by the kit and the recipe as entered into BeerSmith. Both were using LME. Kit recipe was Coopers Light LME and BeerSmith recipe was Briess Golden Light LME. My question was why was there a .008 to .010 difference between the estimated gravity provided by the recipe and the actual starting gravity.
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Bob BanksJul 3 '11 at 17:19

I've never seen that happen when the brewer paid as much attention as you have. I think the only real variable here is the extract-- could be there was a higher sugar content than expected. I can only imagine that making extract is a somewhat inexact science-- perhaps it was a slightly more sugary extract than advertised? The only way to know for sure is to relax, don't worry, have a homebrew and then brew the recipe again. Maybe next time make up your own grist instead of using extract, gain a bit more control.